<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <script>
      function draw() {
        var c = document.getElementById('c').getContext('2d');

        c.fillStyle = 'red';
        c.fillRect(0, 0, 200, 200);

        c.fillStyle = 'lime';
        c.fillRect(0, 0, 100, 100);
      }
    </script>
  </head>
  <body onload="draw();">
    <canvas id='c' width='200' height='200'></canvas>
  </body>
</html>
